In many transplantation type situations, there is concern for differences between the allotype, especially the HLA type, of a cell source and the cell recipient. In situations where allogeneic cells or tissue are taken from a donor and introduced into a recipient, it is desirable that the donor and recipient be as closely HLA matched as possible. The presence in the patient serum of antibodies against HLA antigens of the donor (donor specific crossmatch) or against a high percentage of HLA alleles (PRA testing) predicts a high risk of graft rejection.
The determination of HLA phenotype (H typing) is useful in numerous situations such as transplantation, platelet transfusion and forensic or paternity testing. The standard technique for HLA typing and detection of anti-HLA antibodies is microlymphotoxicity, where serum containing antibodies is incubated with HLA antigen-expressing lymphocytes, then with complement. The level of cytotoxicity is then estimated by discriminating between dead and viable cells using various dyes. This method has numerous disadvantages: it is labor intensive, time consuming, requires isolation of cells, requires viable cells, is nonspecific for HLA, and requires a subjective evaluation. Flow cytometry may also be used but requires a large number of cells and expensive instrumentation.
It is therefore of interest to provide alternative techniques which can be performed simply, can be automated, do not share the shortcomings described above, provide a readily discernible result which is significant for the prognosis of graft acceptance, and comparable to data from existing tests.